4 CHAPTER 1 The Environmental Challenges We Face
at this level of poverty. Poverty is associated with a short
life expectancy, illiteracy, and inadequate access to health
services, safe water, and balanced nutrition.
The world population may stabilize toward the end
of the 21st century, given the family planning efforts
that are currently under way. Population experts at the
Population Reference Bureau have noticed a decrease
in the fertility rate worldwide to a current average of
2.5 children per woman, and the fertility rate is projected
to continue to decline in coming decades.
The fertility rate varies from country to country, from
1.7 in highly developed countries to 4.5 in some of the
least developed countries. Population experts have made
various projections for the world population at the end of
the 21st century, from about 7.7 billion to 10.6 billion, de-
pending primarily on how fast the fertility rate decreases.
No one knows whether Earth can support so many
people indefinitely. Finding ways for it to do so represents
one of the greatest challenges of our times. Among the
tasks to be accomplished is feeding a world population
considerably larger than today’s without destroying the
biological communities that support life on our planet.
The quality of life available to our children and grand-
children will depend to a large extent on our ability to
develop a sustainable system of agriculture to feed the
world’s people.
A factor as important as population size is a popu-
lation’s level of consumption, which is the human use
of material and energy. Consumption is intimately con-
nected to a country’s economic growth, the expansion
in output of a nation’s goods and services.
The world’s economy is growing at an enor-
mous rate, yet this growth is unevenly distrib-
uted across the nations of the world.The Gap Between Rich
and Poor Countries
Generally speaking, countries are divided into
rich (the “haves”) and poor (the “have-nots”).
Rich countries are known as highly developed
countries. The United States, Canada, most
of Europe, and Japan, which represent about- Distinguish among highly developed countries,
moderately developed countries, and less
developed countries. - Relate human population size to natural
resources and resource consumption. - Describe the three factors that are most
important in determining human impact on the
environment.
T
he satellite photograph in Figure 1.1a is a
portrait of about 450 million people. The
tiny specks of light represent cities, and
the great metropolitan areas, such as New
York City along the northeastern seacoast, are ablaze
with light. This represents the most significant factor
impacting the health of Earth’s environment: a large and
growing human population.
In 2011 the human population as a whole passed 7
billion individuals. Not only is this number incompre-
hensibly large, but our population has grown this large
in a very brief span of time. In 1960 the human popu-
lation was only 3 billion (Figure 1.1b). By 1975 there
were 4 billion people, and by 1987 there were 5 billion.
The more than 7 billion people who currently inhabit
our planet consume vast quantities of food and water,
occupy or farm much of the most productive land, use
a great deal of energy and raw materials, and produce
much waste.
Despite most countries’ involvement with family plan-
ning, population growth rates don’t change
overnight. Several billion people will be added
to the world in the 21st century, so even if we
remain concerned about population and even
if our solutions are very effective, the coming
decades may very well see many problems.
On a global level, nearly one in four people
lives in extreme poverty (Figure 1.1c). By one
measure, living in poverty is defined as having
a per person income of less than $2 per day,
expressed in U.S. dollars adjusted for purchas-
ing power. About 3.3 billion people—nearly
half of the world’s population—currently live
Human Impacts on the Environment
LEARNING OBJECTIVES
poverty A condition
in which people are
unable to meet their
basic needs for food,
clothing, shelter,
education, or health.
highly developed
countries Countries
with complex indus-
trialized bases, low
rates of population
growth, and high per
person incomes.